One of many methods of reinforcing rock is to reinforce the rock with reinforcing bars embedded in a solidified fixing material. The fixing material is defined as any suitable bonding for example cement or two component resin.
According to a method using resin cartridges, a hole is drilled in the rock at first and one or several resin cartridges are injected in the hole. Each cartridge comprises at least two closed chambers containing one component each. Then, a reinforcing bar is introduced into the hole during rotation. The rotating reinforcing bar is during the introduction pushing the resin cartridges such that the cartridge compartments tear up and the two components are mixed by the rotating reinforcing bar. Mixing the components forms a compound, which hardens and is solidified during the rotation, usually in one or some minutes. The bolt is threaded in the outer end and a nut and a plate are attached to the bolt end to protect the hole and tension the bolt as a final step.
One way of injecting resin cartridges is to shoot the cartridges into a drilled hole through an injection pipe by the force of compressed air. The injection pipe is usually in the form of a stiff thin-walled plastic tube and is connected to a first end of a hose. The injection pipe is moved into the drill hole by a feeding device. Resin cartridges are placed in the hose and shoot into the drill hole by the compressed air supplied in the other end of the hose.
The dimension of the resin cartridges varies, but can have a diameter of e.g. 20-35 mm and a length of 400-500 mm in the case of a drill hole with a diameter of 30-40 mm.
One example, in injecting a resin cartridge with a diameter of 20 mm in a drill hole with the diameter 30 mm an injection pipe with the inner diameter of about 22 mm and outer diameter of about 26 mm is used.
Cement can be used instead of resin for fixing the reinforcing bar. Instead of shooting resin cartridges into the drill hole via the injection pipe, it is possible to pump the cement into the hole via the hose and the injection pipe.
A problem with the injection devices of the kind described above is that a drill hole can be damaged around the orifice of the drill hole and a distance into the rock, due to earlier blasting activities. In the case of resin cartridges, it causes the resin cartridges to get stuck in the entrance of the drill hole or alternatively on the way into the drill hole. In the case of cement, it causes the cement to leak out of the hole.
Another problem is when the fixing material misses the drill hole. This is a problem irrespective of type of fixing material.
U.S. Pat. No. 4,708,533 teaches a device for guiding a concrete feeding hose. The concrete feeding hose is therein passed by means of a feeder from a reel into a guide head supported on a feeding beam of a drilling equipment and further through the guide head into a hole drilled in the rock, and is passed back on to the reel in proportion as the hole is filled. In order to protect the feeder of the concrete feeding hose against dirt and mechanical damage, the concrete feeding hose is pushed into the guide head through a flexible guiding means.
Thus, there are needs to secure the insertion of fixing material into a drill hole during rock bolting to achieve an effective and high quality rock bolting.
These needs cannot be fulfilled by the injection device according to the above-mentioned prior art.